Essential requirements on a modern plain bearing are high thermo-mechanical load-bearing capacity and a good slip. The first mentioned feature requires a material having a high thermal stability and strength, while soft materials are to be used for a good slip in the region of slide velocities from 15 m/s and above. These requirements are met particularly by multilayer bearings having a soft overlay and a very strong bearing metal layer of bronze or aluminium materials. The overlay which has a particularly good slip is composed, depending upon the method of manufacture, mostly of lead with 8-20% by weight of tin and 2-6% by weight of copper, while occasionally also up to 10% by weight of copper and other metals may be included. Other overlays are also known, such as SnSb7-alloys or PbIn6-alloys.
Such a plain bearing is described in DE-PS 27 22 144. The overlay of the bearing described therein is lead-based with 10-20% by weight of tin and up to 10% by weight of copper. It has been found that permanent load-bearing capacity may be increased with a higher content of copper and tin. It has also been shown, however, that this overlay may be produced by electro-chemical deposition only with difficulties, because electrolytic solutions containing a high proportion of Sn are unstable and that the increase of permanent load-bearing capacity is followed by increased hardness so that increased abrasion of the shaft may take place. It is therefore desirable to increase the proportion of tin in the overlay.